Attempt four at landing the "histogram.h removed from message_loop.h" patch.

net/base/net_log.h

 // Copyright (c) 2010 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef NET_BASE_NET_LOG_H_
 #define NET_BASE_NET_LOG_H_
 
 #include <string>
 #include <vector>
 
 #include "base/basictypes.h"
 #include "base/ref_counted.h"
-#include "base/scoped_ptr.h"
-#include "base/time.h"
 
 class Value;
 
+namespace base {
+class TimeTicks;
+}
+
 namespace net {
 
 // NetLog is the destination for log messages generated by the network stack.
 // Each log message has a "source" field which identifies the specific entity
 // that generated the message (for example, which URLRequest or which
 // SocketStream).
 //
 // To avoid needing to pass in the "source id" to the logging functions, NetLog
 // is usually accessed through a BoundNetLog, which will always pass in a
 // specific source ID.
@@ skipping 194 matching lines @@
   virtual Value* ToValue() const;
 
  private:
   const char* name_;
   const NetLog::Source value_;
 };
 
 }  // namespace net
 
 #endif  // NET_BASE_NET_LOG_H_